Integrity testable multilayered filter device

ABSTRACT

The present invention relates to a device having two or more separate filtration layers that can be independently tested for integrity yet which allow for serial filtration through the two or more layers to obtain the desired characteristics such as retention. The device is made of two or more filtration areas, each containing one filter layer. Each area has one filtration layer and a first endcap bonded to a first end of the filter and a second endcap bonded to a second end of the filter. The areas are arranged concentrically around each other such that the first area is inward of the second area which is inward of a third area and the like. Each area is formed separately and integrity tested separately before final assembly. The first area is slid into the inside of the second area and then the two endcaps are either bonded to each, bonded to a third overall endcap or overmolded by a third endcap.

CROSS REFERENCE TO RELATED APPLICATIONS

The present utility patent application claims the benefit of U.S.Provisional Patent Application No.: 60/725,442, filed on Oct. 11, 2005.The entire contents of which are incorporated herewith in entirety.

The present invention relates to a device containing multiple layers offilters or membrane that is capable of being integrity tested. Moreparticularly, it relates to a device containing multiple layers offilters or membrane each of which is capable of being integrity testedindividually.

BACKGROUND OF THE INVENTION

Some filter devices contain two or more layers of filter or membranesandwiched together in order to gain certain performance characteristicssuch as retention. It is important that each layer remain integral anddefect free throughout the assembly process and during its use.

Normally integrity testing is done to the finished product containingthe multiple layers through an air diffusion test. This test wets outthe filter layers with a suitable liquid, such as water, alcohol ormixtures of the two (depending on whether the filter is hydrophilic orhydrophobic, the fluid used to test for integrity and the like). A gas,gases or liquid at a set pressure(s) is applied to one side of thewelted membrane and its flow on the other side is measured. If the flowincrease downstream is too quick or at a low pressure, this indicatesthat there is a defect in the filter or its sealing into the device. Theproblem with using this test in devices with multiple layers of membraneis that only the overall device is tested and the test can only indicateif there is a defect in all the layers. A defect in one layer may notprovide one with a conclusive indication of a defect especially if thelast layer is integral.

What is needed is a device that allows one to independently test eachlayer of membrane of an integrated multilayered device. The presentinvention allows one the ability to do so.

SUMMARY OF THE INVENTION

The present invention relates to a device having two or more separatefiltration layers that can be independently tested for integrity yetwhich allow for serial filtration through the two or more layers toobtain the desired characteristics such as retention. The device makessubassemblies of each layer and tests each layer for integrity before itis formed into the final device format.

The device is made of two or more filtration areas, each containing onefilter layer. Each area has one filtration layer and a first endcapbonded to a first end of the filter and a second endcap bonded to asecond end of the filter. The areas are arranged concentrically aroundeach other such that the first area is inward of the second area whichis inward of a third area and the like. Each area is formed separatelyand integrity tested separately before final assembly. The first area isslid into the inside of the second area and then the two endcaps areeither bonded to each, bonded to a third overall endcap or overmolded bya third endcap.

A process for making the device is also disclosed. Here a first filterpack is formed of a filter, preferably pleated to increase surface area,which is preferably cylindrical in form and having its two verticaledges (seam) joined together in a liquid tight arrangement. The firsthorizontal end of the filter is liquid tightly bonded to a first endcapand the second horizontal end of the filter is liquid tightly bonded toa second endcap. The first pack is then tested for integrity using anintegrity test such as an air-water diffusion test by wetting thefilter, applying a gas under pressure to one side of the filter, andmeasuring the flow of air on the other side of the filter. Othernon-destructive integrity tests can also be used. Upon successfulcompletion of the integrity test, a second pack is formed the same wayas the first pack. This pack has an inner dimension larger than theouter dimension of the first pack so as to form a concentric arrangementof the packs around each other. The second pack is then integrity testedand if it passes, the two packs are finally assembled so that the firstpack is inside the second pack which concentrically surrounds the firstpack. If desired additionally layers can be formed concentrically aroundthe first two.

These and other embodiments will become obvious to one of ordinary skillin the art from the specification and claims below.

IN THE DRAWINGS

FIG. 1 shows a first embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a multilayered filter device whereineach layer is formed separate from the other layers in a subassembly,each having a first and second endcap. A central porous core and anoutlet are also used. Each layer is then integrity tested and if theypass, they are assembled concentrically around each other and are sealedto each to form a liquid tight device. Preferably, an outer poroushousing is sealed outside the last filter layer and any fluid enteringthe housing must flow through each filter layer and then the core beforeexiting the outlet.

FIG. 1 shows a first embodiment of the present invention with twolayers. More than two layers can be made by the present invention aswell. The first filter layer 2 is sealed along its vertical edges (notshown) preferably by a seam (not shown) as is well-known in the art. Thetop horizontal surface 4 of the filter layer 2 is sealed to a first endcap 6 such as by polymer adhesion, solvent bonding or adhesives.Likewise the bottom horizontal surface 8 of the filter layer 2 is sealedto a second end cap 10 such as by polymer adhesion, solvent bonding oradhesives. A porous core 12 forms the inner surface of the first filterlayer in this embodiment although the core may be a separate piece ormay be part of another piece such as the outlet end cap (describedbelow) if desired.

As shown the first filter layer 2 is preferably cylindrical in shape,although other cross-sectional shapes such as oval, triangular orpolygonal can be used. Preferably the first filter layer 2 is pleated toincrease the available surface area.

Arranged concentrically outside around the first filter layer 2 is asecond filter layer 20. The second layer 20 is preferably cylindrical inshape although other cross-sectional shapes such as oval, triangular orpolygonal can be used and it preferably has the same shape as the firstfilter layer 2. Preferably the second filter layer 20 is pleated toincrease the available surface area. The second filter layer 20 issealed along its vertical edges (not shown) preferably by a seam (notshown) as is well-known in the art. The top horizontal surface 22 of thesecond filter layer 20 is sealed to a first end cap 24 such as bypolymer adhesion, solvent bonding or adhesives. Likewise the bottomhorizontal surface 26 of the second filter layer 20 is sealed to asecond end cap 28 such as by polymer adhesion, solvent bonding oradhesives. Preferably a porous spacer layer 30 is placed adjacent theinner surface of the second filter layer 20 and sealed to the top andbottom end caps 24 and 28.

As shown, the inner edges of the first and second end caps 6, 10 of thefirst filter layer 2 are liquid tightly sealed to the respective outersurfaces of the core 12. The inner edges of the first and second endcaps24, 28 of the second filter layer 20 are liquid tightly sealed to therespective outer surfaces of the first and second end caps 6, 10 of thefirst filter layer 2. Arranged concentrically outward and around thesecond filter layer 20 is a porous cartridge housing 32 that is liquidtightly sealed to the outer edges of the endcaps 24, 28 of the secondfilter layer 20. A top closed cartridge end cap 34 is sealed to thehousing 32, and top end caps 6, 24 of the first and second filter layers2, 20. A bottom cartridge end cap 36 having an outlet 38 is sealed tothe housing 32 and the bottom end caps 10 and 28 of the first and secondfilter layers 2, 20 to complete the cartridge.

In this manner, liquid which enters the housing 32 must flow through thesecond 20 and then the first filter layer 2 before entering the core 12and leaving the filter through the outlet 38.

As mentioned above, the present invention may have more than two layerswith each layer being assembled and arranged concentrically outward ofthe last. Once the outer most filter layer has been formed and sealedthe porous outer housing and top and bottom cartridge end caps areapplied.

A method of making the present device is to form the first layer as asubassembly comprised of at least the filter material and the top andbottom end caps. If desired, the core may be included as the inner wallof the subassembly or it may be a separate piece or incorporated as partof the bottom cartridge endcap. The second, and if desired, additionallayers, are then likewise formed as subassemblies of filter and at leasttop and bottom end caps. Preferably each additional subassembly has aporous spacer or support layer as its inner wall.

The inner diameter of an outer layer is substantially the same diameter(although it may be slightly smaller depending upon the sealing methodused (discussed below) as the outer diameter of the layer inward of itor of the core when referring to the first filter layer. At best thereshould be a slight interference fit between the adjacent layers as theyare assembled together. In this manner, there is a close fit between thesubassemblies so that they can be sealed together in a liquid tightmanner.

As each layer can be independently tested for integrity, one can use anyconventional test such as the air/water diffusion test in which themembrane is wet and a gas is applied to one side of the membrane at aset pressure or range of pressures. The flow of the gas is measured onthe other side of the membrane to determine whether the layer isintegral or if it has a defect such as a pin hole or a defective seal.

Alternatively, one can use a more sophisticated and sensitive test suchas a binary gas test as claimed in a co-pending application filed thisday entitled “Methods and Systems for Integrity testing of PorousMaterials” by John Lewnard. In this test, the selected filter layer iswetted with a liquid that is suitable for the binary gases used. Forexample one can use water, alcohol, mixes of water and alcohol and thelike depending upon the gases selected. Two gases are chosen such thatone has a high solubility in the liquid of choice and the other has alower solubility in that same liquid. Selected gases include but are notlimited to carbon dioxide, Freon, sulfur hexafluoride or other perfluorogases, noble gases and the like. The binary gas mixture is introduced ina predetermined amount relative to each other and the amount of one orboth of the gases is measured by the detection device such as a gaschromatograph or a mass spectrometer on the downstream side of thefilter layer to determine whether there is a shift in the relativeamount of each gas in the detected gas stream. Where the measured amountof gas differs from the predetermined amount of gas initially added tothe system, a defect is detected. If no difference in concentration isfound, the layer is determined to be integral. Integral, when referringherein to a porous material, means non-defective. The predeterminedamount may be, for example, the amount of gas calculated to diffusethrough the integral, wetted porous material at a given temperature andpressure. The given temperature and pressure may be the temperature andpressure under which the test is conducted.

Another method of testing integrity is to use a liquid-liquid porometrytest as shown in U.S. Pat. Nos. 5,282,380 and 5,457,986 (DiLeo) whichmay also be used in the present invention.

The method used for testing integrity is not critical to the invention.Any method that provides one with a suitable value of integrity andwhich is not destructive to the device can be used.

Once all the layers have been made and successfully tested, they can beassembled. The easiest method is to simply slide the first layer intothe hollow center of the second layer, slide the combined first andsecond layer into the third layer, etc. Each pair of layers can besealed to each other before continuing to add any other layers if usedor they can all be sealed at once. A variety of methods are known forsealing plastics to each other and include but are not limited toadhesives, solvent bonding, heat or ultrasonic bonding and the like.

After all the layers have been assembled and sealed to each other, thetop and bottom endcaps are all sealed to a respective cartridge endcapand the outer housing to complete the assembly.

Alternatively, one can slide the subassemblies together, slide an outerhousing over the outermost layer and then place the entire assembly intoa mold and injection mold or overmold the cartridge endcaps over theendcaps of the layers and the housing to create a liquid tight sealingarrangement.

The device and methods of the present invention can be used with anyfilter media of any size that is capable of being integrity tested usinggases or liquids. They may be for example woven or non-woven filters orcast porous membranes. The filter media may be a microporous,ultrafiltration (UF), nanofiltration or reverse osmosis membrane formedof a polymer selected from olefins such as polyethylene includingultrahigh molecular weight polyethylene, polypropylene, EVA copolymersand alpha olefins, metallocene olefinic polymers, PFA, MFA, PTFE,polycarbonate, vinyl copolymers such as PVC, polyamides such as nylon,polyesters, cellulose, cellulose acetate, regenerated cellulose,cellulose composites, polysulphone, polyethersulphone, polyarylsulphone,polyphenylsulphone, polyacrylonitrile, polyvinylidene fluoride (PVDF),and blends thereof. The membrane selected depends upon the application,desired filtration characteristics, particle type and size to befiltered and the flow desired.

The other filter components such as end caps, inlets, outlets, housings,cores, ports, valves, etc., can be made of a variety of materials, suchas metal, ceramic, glass or plastic. Preferably, the components areformed of plastics, more preferably thermoplastics, such as polyolefins,especially polyethylene and polypropylene, homopolymers or copolymersthereof, ethylene vinyl acetate (EVA) copolymers; polycarbonates;styrenes; PTFE resin; thermoplastic perfluorinated polymers such PFA;nylons and other polyamides; PET and blends of any of the above.

1. A serial filtration device having opposing open and closed ends,including two or more concentric cylindrical filter layers wherein eachfilter layer is capable of being independently integrity tested beforebeing assembled into the filtration device, comprising: a.) two or moreconcentric cylindrical layers of filters including, a first filter layerhaving a first and second two vertical edge joined together in a liquidtight arrangement, a first horizontal end of the first filter layerbeing liquid tightly bonded to a first endcap and a second horizontalend of the first filter layer being liquid tightly bonded to a secondendcap; a second filter layer having a first and second two verticaledge joined together in a liquid tight arrangement, a first horizontalend of the second filter layer being liquid tightly bonded to a firstendcap and a second horizontal end of the second filter layer beingliquid tightly bonded to a second endcap; b.) a porous spacer layerlocated between the first and second filter layers, being liquid tightlybound to the first and second endcaps of the second filter layer; c.) aporous core, a top closed endcap and a bottom open endcap having anoutlet for the filter device; d.) a closed top cartridge endcap; e.) anopen bottom cartridge endcap including a filtered fluid outlet forfiltered fluids exiting the filter device; wherein the first filterlayer being arranged concentrically around the core and outlet of thedevice and having an inner diameter equal to or larger than an outerdiameter of the core; wherein the second filter layer having an innerdiameter equal to or larger than an outer diameter of the first filterlayer and being arranged concentrically around the first filter layer;f.) the first filter layer first endcap being bonded in a liquid tightmanner to the core and to the closed top cartridge endcap, and the outeredges of the first filter layer first endcap being bonded in a liquidtight manner to the inner edges of the second filter layer first endcap,wherein the second filter layer first endcap being bonded in a liquidtight manner to the closed top cartridge endcap, a; g.) the first filterlayer second endcap being bonded in a liquid tight manner to the coreand to the open bottom cartridge endcap, and the outer edges of thefirst filter layer second endcap being bonded in a liquid tight mannerto the inner edges of the second filter layer second endcap, wherein thesecond filter layer second endcap is bonded in a liquid tight manner tothe open bottom cartridge endcap; h.) a porous outer cartridge housingarranged concentrically around an outer periphery of the second filterlayer and bonded in a liquid tight manner to, 1) the outer edges of thesecond filter layer first and second endcaps, 2) the open bottomcartridge endcap, and 3) the closed top cartridge endcap, wherein theserial filtration device includes opposing open and closed ends suchthat during liquid filtration a liquid must enter the filtration devicei) through the porous outer cartridge housing, ii) flow through thesecond filter layer, iii) flow through the porous spacer layer, iv)followed by the liquid flowing flow through the first filter layer, v)into the core, and vi) exit the filtration device through the openoutlet in the bottom open endcap.
 2. The filtration device according toclaim 1, wherein the first and second filter layers are both pleated. 3.The filtration device according to claim 1, wherein the first filterlayer is a material selected from the group consisting of a wovenfilter, a non-woven filter or a cast porous membrane.
 4. The filtrationdevice according to claim 1, wherein the first filter layer is selectedfrom the group consisting of a microporous filter, ultrafiltrationfilter, nanofiltration filter, or reverse osmosis membrane.
 5. Thefiltration device according to claim 4, wherein the first filter layeris a polymer material selected from the group consisting of polyolefins,polyethylene, ultrahigh molecular weight polyethylene, polypropylene,ethylene vinyl acetate copolymers, alpha olefins, metallocene olefinicpolymers, PFA, MFA, PTFE, polycarbonate, vinyl copolymers, PVC,polyamides, nylon, polyesters, cellulose, cellulose acetate, regeneratedcellulose, cellulose composites, polysulphone, polyethersulphone;polyarylsulphone, polyphenylsulphone, polyacrylonitrile, polyvinylidenefluoride, and blends thereof.
 6. The filtration device according toclaim 1, wherein the second filter layer is a material selected from thegroup consisting of a woven filter, a non-woven filter or a cast porousmembrane.
 7. The filtration device according to claim 1, wherein thesecond filter layer is selected from the group consisting of amicroporous filter, ultrafiltration filter, nanofiltration filter, orreverse osmosis membrane.
 8. The filtration device according to claim 7,wherein the second filter layer is a polymer material selected from thegroup consisting of polyolefins, polyethylene, ultrahigh molecularweight polyethylene, polypropylene, ethylene vinyl acetate copolymers,alpha olefins, metallocene olefinic polymers, PFA, MFA, PTFE,polycarbonate, vinyl copolymers, PVC, polyamides, nylon, polyesters,cellulose, cellulose acetate, regenerated cellulose, cellulosecomposites, polysulphone, polyethersulphone, polyarylsulphone,polyphenylsulphone, polyacrylonitrile, polyvinylidene fluoride, andblends thereof.
 9. A cylindrical filter cartridge having opposing openand closed ends, comprising: a.) a cylindrical inner porous core; b.) acylindrical first filter arranged concentrically around the core having,a first horizontal surface, and a second horizontal surface, c.) a firstendcap and second endcap each having outer edges, the first horizontalsurface and the porous core are bonded in a liquid tight manner to thefirst endcap, and the porous core and the second horizontal surface arebonded in a liquid tight manner to the second endcap, d.) a porousspacer layer arranged concentrically around the first filter; e.) acylindrical second filter arranged concentrically around the porousspacer layer having and outer periphery, a third horizontal surface, anda fourth horizontal surface; f.) a third endcap and fourth endcap eachhave inner edges and the outer edges of the first endcap are bonded in aliquid tight manner to the inner edges of the third endcap, and theouter edges of the second endcap are bonded in a liquid tight manner tothe inner edges of the fourth endcap, wherein the edges of the endcapsare bonded directly together by a method selected from the groupconsisting of solvent bonding, adhesive bonding, heat bonding andultrasonic bonding, wherein the third horizontal surface is bonded in aliquid tight manner to the third endcap, and the fourth horizontalsurface is bonded in a liquid tight manner to the fourth endcap, whereinthe porous spacer layer is bonded in a liquid tight manner to the thirdand fourth endcaps; g.) a closed top fifth endcap wherein the firstendcap and the third endcap are each bonded in a liquid tight manner tothe fifth endcap; h.) an opened bottom sixth endcap having a fluidoutlet for filtered fluids exiting the filter device, the second endcapand the fourth endcap are each bonded in a liquid tight manner to theopened bottom sixth endcap; and i.) a cylindrical porous outermosthousing arranged concentrically around the outer periphery of the secondfilter and bonded in a liquid tight manner to, 1) the outer edges of thethird and fourth endcaps, 2) the closed fifth endcap, and 3) the opensixth endcap, wherein each filter is capable of being independentlyintegrity tested before being assembled into the filtration devicehaving opposing open and closed ends, wherein the serial filtrationdevice includes opposing open and closed ends such that during liquidfiltration a liquid must enter the filtration device i.) through theporous outer cartridge housing, ii.) flow through the second filterlayer, iii.) flow through the porous spacer layer, iv.) followed by theliquid flowing flow through the first filter layer, v.) into the core,and vi.) exit the filtration device through the open outlet in thebottom open endcap.